Tool steels and stellites or hard metals are generally characterised by high contents of carbon, chromium, cobalt, molybdenum, vanadium and tungsten. These elements, and the corresponding carbides, give the material the necessary strength, in particular wear resistance and hardness. However, this is mostly at the expense of toughness, and is associated with a corresponding increase in resistance to deformation.
High deformation resistance precludes both cold-working and also conventional hot-working as methods for producing the finished contour, so that, only initial shaping by ingot casting or continuous casting, followed by rolling or forging, or by casting into a mould or compacting from powder, come into consideration. These processes however generally require the initially formed part to be machined to the finished contour and size. But it is just in the case of wear-resistant parts that this causes difficulties, inasmuch as the machining requires the use of tools having substantially greater wear resistance than that of the part to be machined. Moreover machining involves substantial loss of material. Substantial working costs are therefore incurred without always obtaining good surface finish.
Added to this are disadvantages specific to the process such as the high energy cost of hot-rolling and -forging, or impairment of surface quality by intensive oxidation of the alloys. A further disadvantage, particularly in respect of intricate finished shapes, is the mostly inadequate flowability during both initial shaping and casting in moulds. This leads to starting pieces that differ considerably from the finished part and therefore require so much machining that substantial losses of material occur. The associated costs are quite considerable on account of the high content of expensive alloying elements in the material concerned. In addition the high resistance to deformation results in high deformation forces being needed, and thus in correspondingly costly working equipment and high energy costs.